Sag-resistant compositions

ABSTRACT

Sag-resistant, pumpable compositions are described which comprise a liquid material dispersed throughout a crosslinked polymer matrix. The liquid material may be a polymerizable material or a polymer-containing material. The compositions of the invention have very broad utility, depending upon the particular ingredients present.

BACKGROUND OF THE INVENTION

This invention relates to flow control of liquid compositions.

In many applications for adhesives it is necessary, or highly desirable,to place the adhesive on a vertical or inclined surface prior to bondinganother material to such surface. Similarly, when using various types ofsealants, it is necessary to place the sealant on a vertical or inclinedsurface. There are many instances of this in building construction andmanufacturing operations. However, when placing liquid adhesives, orsealants, on vertical or inclined surfaces, the adhesives either flowoff or sag considerably before a material can be bonded to the surfaceby means of the adhesive, and liquid sealants tend to flow off or sagconsiderably before they become cured.

Although there are adhesives and sealants available which are not inliquid form, the liquid adhesives and sealants are generally preferredfor many applications because they wet out the surfaces of the materialsto which they are to be adhered, thereby promoting very good adhesion.

Various techniques have been used previously in order to thicken liquidmaterials or to suspend particulate matter such as fillers. For example,a common technique involves addition of small particle inert fillers(such as clay, talc, fumed silica, asbestos and the like) in order tothicken or body a liquid composition (such as an adhesive or sealant).The use of such fillers relies upon particle-particle interaction. Thereare many inherent disadvantages associated with the use of such fillers.

Although such fillers do impart thixotropy to a liquid composition, theviscosity of the composition often does not increase rapidly aftershearing forces are removed. Furthermore, the fillers must be intimatelymixed or compounded with the other ingredients in the composition andthis requires use of a significant amount of energy. It is also possibleto under-mix or over-mix such compositions; accordingly, the degree ofmixing must be carefully controlled.

Moreover, such fillers may be leached out of the composition, or breakdown, on exposure of the composition to the environment during use.Also, some of such fillers have only specific application, i.e. not allof such fillers are useful in all types of compositions. Additionally,the effectiveness of some fillers may be negatively affected by thepresence of other ingredients. Furthermore, it is often difficult toobtain the proper color desired for the ultimate composition, and it isextremely difficult, if not impossible, to obtain clear compositionshaving the desired properties. Fibrous fillers (such as asbestos) alsotend to impart a grainly consistency to a composition, and the use ofsome of such fibrous fillers constitutes a serious health hazard.

Another type of additive which is often used to thicken materials suchas oils and greases is a metal soap (i.e. a metallic salt.) However,such soaps may be reactive with many types of curable compositions andaccordingly such soaps would tend to interfere with the curing of thecomposition and would therefore detract from the cured properties of thecomposition. Furthermore, the compositions which are bodied with suchsoaps are quite shear sensitive.

Another type of material which has been promoted as a thickener forliquid compositions is that commercially available from NL Industriesunder the "Thixcin" series. Such materials have pendent hydroxyl groupsand accordingly rely upon the effects of hydrogen bonding to impartthickening characteristics. However, such materials do not operateefficiently in the presence of polar solvents. Furthermore, compositionscontaining such materials are very shear sensitive.

A specific technique for thickening comprising synthetic elastomer andelastomer solvent is described in U.S. Pat. No. 3,622,534. The techniquedescribed there involves the formation of urea (by reaction of analiphatic amine with an isocyanate in the presence of the syntheticelastomer and elastomer solvent). However, no crosslinked polymer matrixis obtained. As explained in more detail hereinafter, the compositionsof the present invention require the presence of a crosslinked polymermatrix.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided asag-resistant, pumpable composition comprising a liquid materialdispersed throughout a crosslinked polymer matrix, wherein the liquidmaterial is selected from (a) liquid polymerizable materials, and (b)liquid polymer-containing materials.

The compositions of the invention are characterized by good handlingproperties. Preferably, the compositions have a generally butteryconsistency, and the compositions are much less sensitive to shear andmixing than those which contain small particle fillers. Furthermore, byuse of a crosslinked polymer matrix to impart controllable viscosity orbody to a composition, it is possible to obtain clear products becauseno fillers are required. Also, the crosslinked polymer matrix is notaffected by the polarity of the ingredients present in the composition(whereas high polarity of ingredients may render some conventionalthickeners inefficient). Accordingly, the crosslinked polymer matrix maybe used predictably to impart sag-resistance to a myriad ofcompositions.

Moreover, the crosslinked polymer matrix will not leach out of thecompositions or be significantly affected by the environment in whichthe compositions are used.

The term "pumpable" as used herein means that the compositions of theinvention may be caused to flow under some amount of pressure.Accordingly, the compositions may be handled with conventional pumpingequipment during packaging operations or during use of the compositions(e.g the compositions may be packaged in caulking tubes, if desired, andexpelled therefrom by the consumer). Yet, the compositions are alsodesirably sag-resistant, i.e. they exhibit good resistance to flow orsagging on a surface under the influence of gravity immediately afterbeing pumped or caulked into place.

DETAILED DESCRIPTION OF THE INVENTION

The types of liquid materials which are rendered sag-resistant inaccordance with the present invention are selected from liquidpolymerizable materials and liquid polymer-containing materials.

Preferably, the liquid polymerizable materials are selected fromisocyanate-terminated prepolymers, epoxide-containing materials,glycols, and silane-terminated materials. Typical of the usefulisocyanate-terminated prepolymers are those having polyoxyalkylenebackbones, polyepihalohydrin backbones, polythioether backbones,polysulfide backbones, polyester backbones both of the condensation andlactone type, and polyhydrocarbon backbones. Many of these prepolymersare commercially available, e.g. "Vorite" series, available from NLIndustries, "MC-40", available from KJ Quinn, "Spenlite M22-40E",available from Spencer Kellogg. Alternatively, usefulisocyanate-terminated prepolymers may be prepared according to commontechniques which are well known in the art.

Isocyanate-terminated prepolymers are typically caused to polymerize tohigh molecular weight by exposing them to moisture (e.g. moisture in theair). Such prepolymers may also be caused to polymerize by mixing themwith an active-hydrogen-containing material such as glycols, amines,carboxylic acids and the like.

Epoxide-containing materials which are useful in the present inventioninclude diglycidyl ethers of bisphenol A, diglycidyl ethers of novolakresins, epoxidized polybutadiene, cycloaliphatic epoxides, and the like.Many of such epoxides are liquids, although the epoxides which are solidmay also be used provided that they are dissolved in a suitable solvent.

Epoxide-containing materials are cause to polymerize by addition of wellknown curatives such as amine-containing materials, strong acids, andanhydrides. The curatives may be added as a separate material by theconsumer at the time of use of the composition, or the curative may bepresent in the composition in latent form (i.e. the composition may beeither "two-part" or "one-part").

Representative glycols which are useful in the present invention arethose having polyoxyalkylene backbones, polyepihalohydrin backbones,polythioether backbones, polysulfide backbones, polyester backbones bothof the condensation and lactone type, and polyhydrocarbon backbones.Representative glycols which are commercially available include "NiaxPolyol PPG 1025" and "Niax Polyol LHT-240" from Union Carbide; "Polymeg1000 and 2000" from Quaker Chemical Company; "Polycin 51" from NLIndustries; and "Niax Polyol PCP-0210" from Union Carbide.

Glycols are polymerized by reaction with polyisocyanate, which isusually added to the composition at the time of use.

Silane-terminated polymerizable materials which are useful in thepresent invention include any material, organic or inorganic, which hasat least two reactive silane groups thereon. Typical materials havebackbones such as polysiloxane, polyoxyalkylene, polyepihalohydrin,polythioether, polysulfide, polyester (both of the condensation andlactone type), and polyhydrocarbon. One of such materials is prepared byreacting acyloxysilane with hydroxylated siloxanes. The other materialsare prepared by first end-capping hydroxyl-substituted materials havingthe abovedescribed organic backbones using a polyisocyanate-containingmaterial, as is well understood in the art. The resultingisocyanate-terminated material is then reacted withactive-hydrogen-containing silane monomer, in a stoichiometric amount.

Silane-terminated materials as described herein are readily polymerizedby exposure to moisture.

Preferably the liquid polymer-containing materials which are used in thepresent invention are selected from non-crosslinked acrylic polymers (insolvent solution), polyurethane resins (in solvent solution),rubber-resin solvent solutions, silicone oils and lubricating fluids.Typical of the acrylic polymers are polymethylmethacrylate,poly-n-butylmethacrylate, polyethylacrylate, poly-n-butylacrylate, andvarious copolymers thereof. Acrylic polymers are widely available insolid form and in solvent solution form. Typical commercially availableacrylic polymers are the "Lucite" series available from E. I. duPont,and the "Acryloid" series available from Rohm and Haas. Each of theseare available in solid and solvent solution form.

The polyurethanes which are useful may have any type of backbone,although those types of backbones described above with respect toisocyanate-terminated prepolymers are the most common backbones usedherein. Typical commercially available polyurethane resins in solventsolution form are the "Rucothane" series available from Hooker Chemical,and "Permuthane" series available from Beatrice Chemical Division ofBeatrice Foods, and others which are well known. Typical commerciallyavailable solid resins, which may be dissolved in solvents such asketones, acetates, aromatics, dimethylformamide, tetrahydrofuran, andthe like, include the "Estane" series available from B. F. GoodrichChemical, and other well known materials.

Typical rubber-resin solutions which are useful are natural andsynthetic rubbers dissolved in common solvents (such as hydrocarbons,aromatics, ketones, chlorinated esters and the like) along with naturaland synthetic tackifying or reinforcing resins which are well known inthe art.

Typical silicone oils which are useful are those which are promoted foruse as high performance lubricating oils. These materials typically havea siloxane backbone and are relatively inert. Typical commerciallyavailable silicone oils are the "SWS" series available from StaufferWacker.

Typical lubricating fluids which may be used are the commonly availablehydrocarbon, paraffinic, naphthenic or aromatic lubricating oils. Suchmaterials are very well known in the art and are commercially availablefrom a wide variety of companies in the petroleum industry.

When the liquid materials are dispersed throughout the crosslinkedpolymer matrix a sag-resistant, pumpable composition is obtained.Preferably the crosslinked polymer matrix is formed in the presence ofthe liquid materials (i.e. in situ), although it is also possible toform the crosslinked polymer matrix in a solvent, followed by additionof the liquid material thereto with heating and stirring.

The crosslinked polymer matrix may be formed from various monomers.Preferred monomers are those which are polymerizable by a free-radicalmechanism, although other types of monomers may also be used. Preferredfree-radically-polymerizable monomers include polyfunctional acrylicmonomers (such as polyfunctional acrylates, methacrylates, andsubstituted acrylates and methacrylates), divinyl aromatic monomers(such as divinyl benzene and divinyl toluene), polyfunctionalacrylamides) such as N,N'-methylenebisacrylamide), polyfunctionalallylic monomers (such as triallylcyanurate, triallylisocyanurate, andtriallylphosphite), and mixtures thereof. Otherfree-radically-polymerizable monomers may also be added, such asstyrene, ethylacrylate and -methacrylate, butyl-acrylate and-methacrylate, 2-ethylhexylacrylate and -methacrylate, isooctyl-acrylateand -methacrylate, and the like.

Preferably, the crosslinked polymer matrix is derived frompolyfunctional acrylate or methacrylate monomers. Representative ofthese monomers are:

trimethylolpropane triacrylate and trimethacrylate

1,4-butanediol diacrylate and dimethacrylate

diethyleneglycol diacrylate and dimethacrylate

pentaerythritol tetracrylate and tetramethacrylate

1,6-hexanediol diacrylate and dimethacrylate

and other well known polyfunctional acrylates and methacrylates.

Typically the polyfunctional monomer is added to the liquid material andthen polymerized in situ to form a crosslinked polymer matrix. Generallyspeaking, the amount of polyfunctional monomer to be used may vary overa broad range depending upon the initial viscosity of the liquidmaterial and the degree of sag-resistance desired in the finalcomposition. Generally, the amount of monomer added is in the range of0.5% to 20% by weight of the composition. Preferably, sufficient monomeris added such that after the crosslinked polymer matrix is formed thecomposition has increased viscosity and exhibits the desired degree ofsag resistance.

When using free-radically-polymerizable monomers, a small amount offree-radical-generating catalyst or initiator is added to the liquidmaterial, along with the monomer, after which the blended mixture istypically heated at elevated temperature for a time sufficient to obtainsubstantial polymerization of the monomer to form the crosslinkedmatrix. Generally speaking, the amount of catalyst or initiator added isin the range of about 0.25% to 5% based on the weight of the monomer.

Typical of the useful free-radical generating catalysts are azo-typecatalysts, peroxides, hydroperoxides, redox-type catalysts, andphotoinitiators. Representative useful catalysts include2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylpropionitrile, benzoylperoxide, dicumylperoxide, methylethylketone peroxide, cumenehydroperoxide, benzoin methylether, benzoin ethylether, photolyzableorganic halogen compounds described in U.S. Pat. No. 3,617,288, andother catalysts well known in the art.

The compositions of the invention may also include, if desired,antioxidants, U.V. stabilizers, inert extenders, pigments or dyes,wetting agents, adhesion promoters, plasticizers, curatives, and othercommon additives.

The compositions of the invention have very wide utility. For example,the compositions may be used as adhesives, sealants, or coatingsdepending upon the particular type of polymerizable material (orpolymer-containing material) present therein. An additional advantagederived from the present invention is that it is possible to preparecompositions which produce clear products by selecting a crosslinkedpolymer matrix which has an index of refraction which substantiallymatches that of the polymer derived from the liquid polymerizablematerial or the polymer-containing material.

The invention is further illustrated by means of the followingnon-limiting examples in which the term "parts" refers to parts byweight unless otherwise indicated.

EXAMPLE 1

An isocyanate-terminated prepolymer is prepared by the addition of oneequivalent (984 grams) of polypropylene glycol ("PPG 2025", commerciallyavailable from Union Carbide) to two equivalents (174 grams) of toluenediisocyanate, followed by heating for a period of four hours at 80° C. Adry nitrogen purge is maintained during the entire reaction period toprevent reaction of the isocyanate moieties with water. The resultingprepolymer product is permitted to cool to room temperature. Theviscosity of the prepolymer is measured and found to be 6800 centipoiseat 25° C.

To the above prepolymer is added 57.9 grams oftrimethylolpropanetrimethacrylate and 0.58 grams of2,2'-azobisisobutyronitrile. The ingredients are blended together usingmoderate agitation, under constant nitrogen purging to minimize theamount of moisture and oxygen present, and the blended ingredients areheated at 90° C. for one hour. Under such conditions the acrylatemonomer is polymerized in the presence of the prepolymer to form acrosslinked polymer matrix. The resulting product, after being cooled toroom temperature, has a viscosity of 995,000 centipoise and is pumpable.When packaged in an air-tight container the product has prolongedstability.

The product exhibits no sag when semi-circular beads of the producthaving a one-fourth inch (6.4 mm.) radius are disposed on a nearlyvertical panel (5° from vertical).

The product is an excellent adhesive and cures readily when exposed tothe atmosphere.

EXAMPLE 2

The isocyanate-terminated prepolymer of Example 1 is blended with 57.9grams of 1,6-hexanedioldiacrylate and 0.58 gram of2,2'-azobisisobutyronitrile. The ingredients are blended together usingmoderate agitation, under constant nitrogen purging, and the blendedingredients are heated at 90° C. for one hour. Under such conditions theacrylate monomer is polymerized in the presence of the prepolymer toform a crosslinked polymer matrix. The resulting product, after beingcooled to room temperature, has a viscosity of 40,000 cps. and ispumpable. When packaged in an air-tight container the product hasprolonged stability.

The product exhibits no sag when semi-circular beads of the producthaving a one-eighth inch (3.2 mm.) radius are disposed on a nearlyvertical panel (5° from vertical).

The product is an excellent adhesive and cures readily when exposed tothe atmosphere.

EXAMPLE 3

A sag-resistant, pumpable composition is prepared using the procedure ofExample 1 except that 57.9 grams of diethyleneglycoldiacrylate issubstituted for the trimethylolpropanetrimethacrylate. The resultingproduct has a viscosity of 187,500 cps. The product has prolongedstability in air-tight containers.

The product is an excellent adhesive and cures readily when exposed tothe atmosphere.

EXAMPLE 4

A sag-resistant, pumpable composition is prepared using the procedure ofExample 1 except that the polypropylene glycol is replaced with oneequivalent weight of a glycol derived from ricinoleic acid in thepreparation of the isocyanate-terminated prepolymer.

After in situ formation of the crosslinked acrylate polymer, asdescribed in Example 1, the resulting composition exhibits a viscosityof 160,000 cps. The product exhibits minimal sag when semi-circularbeads of the product having a one-fourth inch (6.4 mm.) radius aredisposed on a nearly vertical panel (5° from vertical).

The product is an excellent moisture-curable adhesive.

EXAMPLE 5

A sag-resistant, pumpable composition is prepared using the followingingredients in the amounts stated:

    ______________________________________                                        Ingredient                 Parts                                              ______________________________________                                        Epoxy resin (epoxy equivalent weight 185-200;                                                            700                                                 "Epon 828", commercially available from                                       Shell Chemical Company)                                                      Trimethylolpropanetrimethacrylate                                                                         35                                                2,2'-Azobisisobutyronitrile                                                                              0.35                                               ______________________________________                                    

The above ingredients are blended together, with moderate agitation, forone hour at 90° C. whereby the acrylate monomer is polymerized to form acrosslinked polymer matrix. After cooling the resulting composition to77° F. it exhibits a viscosity of 13,000 cps. The composition exhibitsgood shelf stability and is sag-resistant. A three inch (7.6 cm.) widecoating up to about ten mils (0.25 mm.) thick does not flow whendeposited on a nearly vertical surface (5° from vertical).

The composition is readily cured by addition thereto of amine-functionalthermoplastic polyamide resin ("Versamid", available from General Mills,Inc.).

EXAMPLE 6

To 107.6 grams of an acetoxysilane-terminated silicone prepolymer in99.4 grams of toluene are added, with stirring, 5.4 grams oftrimethylolpropanetrimethacrylate and 0.5 gram of2,2'-azobisisobutyronitrile. The blend is heated at 90° C. for one hour.A dry nitrogen purge is maintained during the reaction period. Undersuch conditions the acrylate monomer is polymerized in situ to form acrosslinked polymer matrix.

The resulting sag-resistant, pumpable product has a viscosity of 28,500centipoise. When packaged in air-tight containers the product hasprolonged stability.

The product exhibits no sag when semi-circular beads of the producthaving a 3/16 inch (4.8 mm.) radius are disposed on a nearly verticalpanel (5° from vertical).

The product is a good sealant and cures when exposed to moisture (e.g.from the air).

EXAMPLE 7

Four hundred grams of poly-n-butylmethyacrylate ("Lucite 2044",commercially available from E. I. duPont) are dissolved in 400 grams oftoluene. To this polymer-containing solution are added, with stirring,20 grams of trimethylolpropane trimethacrylate and 0.2 grams of2,2'-azobisisobutyronitrile. The blend is heated at 90° C. for one hour.

The resulting composition has a viscosity of 350,000 centipoise and ispumpable.

The composition exhibits no sag when semi-circular beads of thecomposition having a 3/16 inch (4.8 mm.) radius are disposed on a nearlyvertical panel (5° from vertical).

The composition, upon drying to remove solvent, produces a translucentsealant or coating.

EXAMPLE 8

Six hundred sixty (660) grams of polyisobutylene ("Vistanex LMMS",commercially available from Exxon Corp.) and 330 grams of polyterpeneresin ("Piccolyte S-100", commercially available from Hercules, Inc.)are dissolved in 660 grams of toluene. To this rubber-resin solution isadded, with stirring, 49.5 grams of trimethylolpropane trimethacrylateand 0.5 gram of 2,2'-azobisisobutyronitrile. The blend is heated at 90°C. for one hour with agitation.

The resulting composition, after cooling, has a viscosity of 126,000centipoise and is pumpable.

The composition exhibits no sag when semi-circular beads thereof havinga 1/4 inch (6.4 mm.) radius are disposed on a nearly vertical surface(5° from vertical). The composition, upon drying to remove solvent, hasutility as an adhesive or sealant.

EXAMPLE 9

To 300 grams of a conventional non-reactive silicone-based polymeric oil("SWS 101"; viscosity of 100 stokes; commercially available fromStauffer Wacker) are added 15 grams of trimethylolpropanetrimethacrylate and 0.15 gram of 2,2'-azobisisobutyronitrile. The blendis heated for one hour at 90° C. with stirring.

The resulting composition has a viscosity of 200,000 centipoise and ispumpable.

The composition exhibits no sag when semi-circular beads thereof havinga radius of 1/8 inch (3.2 mm.) are disposed on a nearly vertical panel(5° from vertical).

The composition is useful as a high viscosity grease.

EXAMPLE 10

Forty-five grams of trimethylolpropane trimethacrylate and 0.45 gram of2,2'-azobisisobutyronitrile are added to 1390.8 grams of toluene. Theblend is heated at 90° C. for three hours using moderate agitation. Agel (viscosity of approximately 1000 centipoise) having good non-sagcharacteristics is obtained.

478.8 grams of the above gelled composition is added to 250 grams of aisocyanate-terminated prepolymer ("Desmodur E-21", commerciallyavailable from Mobay) and 150 grams of a toluene diisocyanate-terminatedprepolymer ("Desmodur E-14", commercially available from Mobay). Theblend is agitated by means of an air stirrer rotating at about 250 rpm.

Excess solvent (toluene) is removed from the blend using vacuumstripping until a non-volatile content of 83% by weight is obtained.

The resulting composition has a viscosity of 17,000 centipoise and ispumpable. The composition exhibits no sag when semi-circular beadsthereof having a 1/8 inch radius are disposed on a nearly verticalsurface (5° from vertical).

The composition has utility as a moisture-curable adhesive.

EXAMPLE 11

Five hundred grams of a polyoxypropylene glycol ("PPG 1025",commercially available from Union Carbide Corp.) are added to 25 gramsof trimethylolpropane trimethacrylate and 0.25 grams of2,2'-azobisisobutyronitrile. The blend is heated at 90° C. for one hourunder moderate agitation.

The resulting composition has a viscosity of 70,000 centipoise and ispumpable. The composition exhibits no sag when semi-circular beadsthereof having a radius of 1/8 inch are disposed on a nearly verticalsurface.

Upon mixing of this composition with polyisocyanate and a Freon blowingagent, it is possible to spray the composition on a vertical surface (toobtain an expanded foam) without sagging or running.

EXAMPLE 12

To 910 grams of the isocyanate-terminated prepolymer prepared as inExample 1 are added 91 grams of divinylbenzene and 0.91 gram of2,2'-azobisisobutyronitrile. The blend is heated for one hour at 90° C.under a constant dry nitrogen purge and with agitation.

The resulting composition has a viscosity of over 1,000,000 centipoiseand is a waxy solid but yet is pumpable.

The composition, which exhibits excellent sag-resistance, has utility asa moisture-curable sealant.

What is claimed is:
 1. A sag-resistant, pumpable, curable compositioncomprising an isocyanate-terminated prepolymer dispersed throughout asynthetic, continuous, crosslinked polymer matrix.
 2. A composition inaccordance with claim 1, wherein said crosslinked polymer matrix isderived from trimethylolpropane trimethacrylate monomer.
 3. Acomposition in accordance with claim 1, wherein said crosslinked polymermatrix is formed in situ.
 4. A composition in accordance with claim 1,wherein said prepolymer has a polyoxyalkylene backbone.
 5. Asag-resistant, pumpable composition comprising a liquidisocyanate-terminated prepolymer material dispersed throughout acontinuous, crosslinked acrylic polymer matrix.
 6. A method forrendering a liquid isocyanate-terminated prepolymer materialsag-resistant comprising dispersing said prepolymer material throughouta continuous, crosslinked acrylic polymer matrix.
 7. A compositionaccording to claim 1, wherein said crosslinked polymer matrix is formedfrom free-radially-polymerizable monomer equivalent to 0.5 to 20% byweight of said composition.
 8. A composition according to claim 1,wherein said crosslinked polymer matrix is formed fromfree-radically-polymerizable monomer equivalent to 0.5 to 10% by weightof said composition.